In recent years, an infrared ray lamp which uses a carbon-based material formed in a rod shape as a heat generating element has been developed. The infrared ray lamp in accordance with a prior art is disclosed in Japanese Patent Publication No. 2001-351762 A. A description will be given of the infrared ray lamp in accordance with the prior art with reference to FIG. 17. FIG. 17 is an elevation showing a structure of the infrared ray lamp in accordance with the prior art. The infrared ray lamp has a transparent silica glass tube 1701 and a heat generating element 1702, and the heat generating element 1702 is sealed in the glass tube 1701.
The heat generating element 1702 is a carbon-based material formed into a long rod shape or plate shape, and is made of a mixed material obtained by adding a resistance value regulating material of a nitrogen combination and an amorphous carbon to a base material of a crystallized carbon such as a black lead or the like. By making the plate width of the heat generating element larger than the plate thickness, an amount of heat output from a surface having a plate width is more than an amount of heat output from a surface having a plate thickness whereby it is possible to apply directivity to a radiation of the heat generating element 1702.
The heat generating element has a first heat generating part 1702a and a second heat generating part 1702b corresponding to an oval region having a thinner plate thickness than the first heat generating part, and can set a temperature distribution in a longitudinal direction of the infrared ray lamp to a desired temperature distribution by changing the temperatures of the first heat generating part 1702a and the second heat generating part 1702b of the heat generating element.
Further, a cross sectional area of a section vertical to an axial direction (a longitudinal direction) is gradually changed along the longitudinal direction in a boundary part between the first heat generating part 1702a and the second heat generating part 1702b by making the second heat generating part 1702b oval, whereby a temperature change in the boundary part becomes slow.
Various precise electronic apparatuses (for example, the copying machine) have a heating apparatus in an inner part thereof. If the heating apparatus installed in the electronic apparatus mentioned above is always set in a heating state, an internal temperature of the electronic apparatus is increased more than necessary, or the heat is expanded to a wider region than a part which is necessary to be heated, so that there is a risk that a reduction of reliability and service life of the electronic apparatus is caused. Accordingly, it is important for securing the reliability and the service life of the electronic apparatus to heat the part which is necessary to be heated locally and only for a time which is required to be heated. Further, it is important that the heat generating element of the heating apparatus does not generate a great rush current.
For example, in the copying machine, it is necessary that the heating apparatus installed for drying a toner attached to a paper switches a width for heating the paper between a time of copying a wide A4 paper and a time of copying a longitudinal A4 paper. In the same manner, there are various electronic apparatuses (for example, a printer or the like) having a plurality of modes in which the heating widths are different. It is important for making the electronic apparatuses compact to make the heating apparatus compact.
The conventional electronic apparatus has a heating apparatus having a structure of inserting a heat generating element formed by winding a tungsten resistance wire spirally into a glass tube and generating heat in an ambient atmosphere. If the conventional heating apparatus is used in a state in which a temperature of a glass tube wall does not reach a predetermined temperature (typically equal to or more than 250° C.), a halogen cycle within the glass tube is not generated, and the tungsten is evaporated to become slim, so that there is a problem that the tungsten generates a disconnection so as to be shortened in a service life. Accordingly, in order to set the glass tube wall to the predetermined temperature, an ON-OFF control method is frequently employed in the electronic apparatus.
A temperature characteristic of the tungsten is a positive characteristic (in which a resistance is small in a normal temperature and the resistance becomes large if the temperature is increased). Accordingly, a large rush current flows first after applying a commercial alternating current power, and there is a risk that the other circuits in the electronic apparatus are damaged at a time of lighting. Since the tungsten heat generating element generates the large rush current every time of turning on and off, a device used in the same circuit is affected. Accordingly, a flicker phenomenon is caused.
Therefore, although a service life of the tungsten heat generating element is changed in accordance with a used temperature, it is only about 5000 hours.
Further, it is necessary to control for heating the part which is necessary to be heated by the tungsten heat generating element to a predetermined temperature, and a problem is generated. For example, at a standby time when the electronic apparatus is not used, it is necessary to warm up for improving a start. At this time, an extra electric power is required for setting the glass tube at a predetermined temperature.
The present invention purposes to provide a compact heating apparatus having a plurality of modes which are different in a heating width, and an infrared ray lamp suitable for the heating apparatus.
The present invention purposes to provide a high reliable electronic apparatus having the above-mentioned heating apparatus.
The present invention purposes to provide a heating apparatus which has a high heating efficiency, can locally heat a part to be heated, can achieve a rated temperature for an extremely short time after starting the heating, reduces a large rush current and flicker at a time of lighting, has a long service life, and can correspond to a plurality of modes having different heating widths, and an infrared ray lamp suitable for the heating apparatus.